AbstractStellar metallicity and planet formation are intimately linked. According to the core accretion planet formation model, low-mass planets are expected to orbit stars with a wide range of metallicities, while giant planets should be more common around metal-rich stars. But the existence of a planet-metallicity relation for the low-mass planets is not yet fully confirmed or quantified observationally.

To address this problem, we have been using HARPS radial-velocity observations to study a sample of metal-poor stars. Our goal is to detect low-mass planets, with masses close to that of the Earth and Neptune, and to estimate their frequency around low-metallicity stars. I will present the latest results of this decade-long search, explain some of the difficulties that stellar activity poses on planet detection, and describe a new algorithm being developedto help with planet detection in radial-velocity data.